Whitney Tilson presented what seemed like a well thought out argument for BP as a long-term investment:
http://www.cnbc.com/id/15840232/?video=1516597145&play=1
IIRC, he still thought 10% chance of going to zero or towards zero, and it wasn't a full position in his diversified portfolio of investments.
I think there was another CNBC (Fast Money yesterday?) clip where he went into more detail about how lawsuit liabilities are likely to be drawn out over 10 years and be watered down over time (I think, but am not sure, he said they would make something obscene amount of profits in the interim).
He also never mentioned upside target once there was clarity on the actual amount of liabilities, and no mention of time frame in ideal or worst case scenario, so no ideal of best and worst case rate of return for risk taken.